Effect of Forward Speed on the Roll Damping of Three Small Fishing Vessels

1994 ◽  
Vol 116 (2) ◽  
pp. 102-108 ◽  
Author(s):  
M. R. Haddara ◽  
S. Zhang
Keyword(s):  
Natural Frequency ◽  
Energy Method ◽  
Function Method ◽  
Experimental Program ◽  
Forward Speed ◽  
Roll Damping ◽  
Fishing Vessels ◽  
Novel Method ◽  
Modified Formula ◽  
Good Agreement

An extensive experimental program has been carried out to estimate roll damping parameters for three models of fishing vessels having different hull shapes and moving with forward speed. Roll damping parameters are determined using a novel method. This method combines the energy method and the modulating function method. The effect of forward speed, initial heel angle and the natural frequency on damping is discussed. A modification of Ikeda’s formula for lift damping prediction is suggested. The modified formula produces results which are in good agreement with the experiments.

The Energy Approach of Elastic-Plastic Fracture Mechanics Applied to the Analysis of the Warm Pre-Stress Effect

2003 ◽  
Author(s):  
Yves Wadier ◽  
M. Bonnamy
Keyword(s):  
Release Rate ◽  
Energy Method ◽  
Ferritic Steel ◽  
Structural Integrity ◽  
Energy Approach ◽  
Experimental Results ◽  
Experimental Program ◽  
Stress Effect ◽  
Integrity Assessment ◽  
Good Agreement

An experimental program was recently carried out in the context of a MPA-EDF collaboration, in order to study the “Warm Pre-Stress” effect on CT25 side-grooved specimens made of 18MND5 (equivalent to A508) ferritic steel. At EDF, an energy approach has been developed and an energy release rate, called Gp, has been defined. Conversely to the J-approach, this energy approach is, in principle, valid in all situations, and can be used in particular to study the “Warm Pre-Stress” effect in RPV structural integrity assessment. For the WPS cycle called “LCF” (Loading + Cooling + Fracture), the comparison to the experimental results and to the results obtained with the Beremin model is very satisfactory, all the results being in a good agreement. For the WPS cycle called “LUCF” (Loading + Unloading + Cooling + Fracture) the results obtained with the energy method, compared to experimental results, show a conservatism which is not very important, anyway smaller than the conservatism obtained with the Beremin model.

scholarly journals A NOVEL METHOD FOR THE M-TERMS OF SHIP WITH FORWARD SPEED

Brodogradnja ◽  
2020 ◽  
Vol 71 (4) ◽  
pp. 95-108
Author(s):  
J.K. Chen ◽  
◽  
W.Y. Duan
Keyword(s):  
Linear Wave ◽  
Forward Speed ◽  
Floating Bodies ◽  
First Order ◽  
Numerical Studies ◽  
Motion Problem ◽  
Novel Method ◽  
The Right ◽  
Wave Induced ◽  
Good Agreement

One of the major difficulties in linear wave-induced ship motion problem with forward speed is how to solve the m-terms accurately. This paper proposes a novel numerical method (Taylor Expansion Boundary Element Method, TEBEM) to compute the m-terms for arbitrary floating bodies. This method treats the m-terms as the Dirichlet type, uses the first-order derivatives terms on the right-handed side of boundary value problem, which is solved by TEBEM method. Numerical studies are performed for the hemisphere, mounted cylinder, and modified KVLCC2 ship models. Compared to the analytical solutions and other numerical results, a good agreement can be obtained by the TEBEM method.

A novel method for single and multiple damage detection in beams using relative natural frequency changes

2019 ◽  
Vol 132 ◽  
pp. 335-352 ◽  
Author(s):  
Ganggang Sha ◽  
Maciej Radzieński ◽  
Maosen Cao ◽  
Wiesław Ostachowicz
Keyword(s):  
Damage Detection ◽  
Natural Frequency ◽  
Novel Method ◽  
Frequency Changes

The Behaviour of Multiple Loops in Torsion

1988 ◽  
Vol 15 (3) ◽  
pp. 149-156 ◽  
Author(s):  
R. A. Cavina ◽  
N. E. Waters
Keyword(s):  
Energy Method ◽  
Strain Energy ◽  
Vertical Axis ◽  
Experimental Measurements ◽  
Complementary Strain ◽  
Radial Axis ◽  
Strain Energy Method ◽  
Good Agreement

The angular stiffness of a multiple looped span, subject to rotation about a vertical axis (torsion) and also to rotation about a horizontal or radial axis (mesio-distal tilt), have been derived using the complementary (strain) energy method. Experimental measurements on enlarged models were in good agreement with the values calculated from the theoretical relationships obtained. The variations in angular stiffness resulting from changes in the loop height, width, and position of clinical sized loops are discussed.

Investigating the vibrational behaviour of a rotating two-blade propeller by using a self-tracking method

2018 ◽  
Vol 233 (3) ◽  
pp. 835-847 ◽  
Author(s):  
Mohammad-Reza Ashory ◽  
Farhad Talebi ◽  
Heydar R Ghadikolaei ◽  
Morad Karimpour
Keyword(s):  
Natural Frequency ◽  
Measurement Errors ◽  
Mode Shapes ◽  
Model Parameters ◽  
Test Results ◽  
Modal Assurance Criterion ◽  
Tracking Method ◽  
Strong Resemblance ◽  
Test Scenarios ◽  
Good Agreement

This study investigated the vibrational behaviour of a rotating two-blade propeller at different rotational speeds by using self-tracking laser Doppler vibrometry. Given that a self-tracking method necessitates the accurate adjustment of test setups to reduce measurement errors, a test table with sufficient rigidity was designed and built to enable the adjustment and repair of test components. The results of the self-tracking test on the rotating propeller indicated an increase in natural frequency and a decrease in the amplitude of normalized mode shapes as rotational speed increases. To assess the test results, a numerical model created in ABAQUS was used. The model parameters were tuned in such a way that the natural frequency and associated mode shapes were in good agreement with those derived using a hammer test on a stationary propeller. The mode shapes obtained from the hammer test and the numerical (ABAQUS) modelling were compared using the modal assurance criterion. The examination indicated a strong resemblance between the hammer test results and the numerical findings. Hence, the model can be employed to determine the other mechanical properties of two-blade propellers in test scenarios.

A Quasi-Greens Function Method for the Bending Problem of Simply Supported Polygonal Shallow Spherical Shells on Pasternak Foundation

2013 ◽  
Vol 353-356 ◽  
pp. 3215-3219
Author(s):  
Shan Qing Li ◽  
Hong Yuan
Keyword(s):  
Function Method ◽  
Homogeneous Boundary Condition ◽  
Fredholm Integral Equations ◽  
Pasternak Foundation ◽  
Boundary Equation ◽  
Spherical Shells ◽  
Simply Supported ◽  
Suitable Form ◽  
Greens Function ◽  
Good Agreement

The quasi-Greens function method (QGFM) is applied to solve the bending problem of simply supported polygonal shallow spherical shells on Pasternak foundation. A quasi-Greens function is established by using the fundamental solution and the boundary equation of the problem. And the function satisfies the homogeneous boundary condition of the problem. Then the differential equation of the problem is reduced to two simultaneous Fredholm integral equations of the second kind by the Greens formula. The singularity of the kernel of the integral equation is overcome by choosing a suitable form of the normalized boundary equation. The comparison with the ANSYS finite element solution shows a good agreement, and it demonstrates the feasibility and efficiency of the proposed method.

A Dynamic Test of Fully Prestressed Concrete Beams

2011 ◽  
Vol 368-373 ◽  
pp. 2483-2490
Author(s):  
Yao Ting Zhang ◽  
Yi Zheng ◽  
Hong Jian Li
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Theoretical Analysis ◽  
Natural Frequency ◽  
Axial Force ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Dynamic Test ◽  
Modified Formula

A dynamic test of two unbonded fully prestressed concrete beams has been conducted. The results indicate that the natural frequency of beams increases with the prestress force, which is opposite to the analytical arguments for homogeneous and isotropic beams subject to axial force. This paper explains the change in frequencies by discussing the change in the elastic modulus. A modified formula is also proposed, and the experimental data agree well with the theoretical analysis.

scholarly journals Stochastic Inverse Identification of Nonlinear Roll Damping Moment of a Ship Moving at Nonzero-Forward Speeds

2012 ◽  
Vol 2012 ◽  
pp. 1-22 ◽  
Author(s):  
S. L. Han ◽  
Takeshi Kinoshita
Keyword(s):  
Nonlinear Damping ◽  
Rolling Motion ◽  
Forward Speed ◽  
Roll Damping ◽  
Nonparametric Approach ◽  
Nonlinear Responses ◽  
Different Types ◽  
Experimental Trials ◽  
And Control ◽  
Ship Rolling

The nonlinear responses of ship rolling motion characterized by a roll damping moment are of great interest to naval architects and ocean engineers. Modeling and identification of the nonlinear damping moment are essential to incorporate the inherent nonlinearity in design, analysis, and control of a ship. A stochastic nonparametric approach for identification of nonlinear damping in the general mechanical system has been presented in the literature (Han and Kinoshits 2012). The method has been also applied to identification of the nonlinear damping moment of a ship at zero-forward speed (Han and Kinoshits 2013). In the presence of forward speed, however, the characteristic of roll damping moment of a ship is significantly changed due to the lift effect. In this paper, the stochastic inverse method is applied to identification of the nonlinear damping moment of a ship moving at nonzero-forward speed. The workability and validity of the method are verified with laboratory tests under controlled conditions. In experimental trials, two different types of ship rolling motion are considered: time-dependent transient motion and frequency-dependent periodic motion. It is shown that this method enables the inherent nonlinearity in damping moment to be estimated, including its reliability analysis.

Investigation of Sensitivity Effect Based on Mass and Stiffness Modification in Automobile Crankshaft

2015 ◽  
Vol 752-753 ◽  
pp. 839-844
Author(s):  
R.M.S. Zetty ◽  
B.A. Aminudin ◽  
L.M. Aung ◽  
M.K. Khalid ◽  
H.M.Y. Norfazrina ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Differential Analysis ◽  
Partial Differential ◽  
Mechanical Parts ◽  
Stiffness Reduction ◽  
Experiment And Simulation ◽  
Good Agreement

A modeling through sensitivity analysis is one of the promising methods to investigate the dynamic characteristics of complex mechanical parts. This study aimed to investigate the effect of sensitivity based on mass and stiffness modification in automobile crankshaft as a function of natural frequency. Verification for the crankshaft model that is used in the experiment and simulation was done and both results showed good agreement and small errors percentage. The modification was also done by reducing the different percentage of crankshaft’s mass and stiffness. Partial differential analysis was used in the sensitivity analysis in order to figure out the natural frequency after every set of modification. According to the results, we also found that there were changes of sensitivity value by changes in mass value but the stiffness value remains unchanged. However, there is no significant effect of stiffness reduction on vibration was found in this research.

Analysis of a Natural Frequency Tracking System for MEMS Fatigue Testing

2001 ◽  
Author(s):  
Xiaotian Sun ◽  
Roberto Horowitz ◽  
Kyriakos Komvopoulos
Keyword(s):  
Control System ◽  
Natural Frequency ◽  
Averaging Method ◽  
Fatigue Testing ◽  
Tracking System ◽  
Frequency Tracking ◽  
At Resonance ◽  
Mems Resonator ◽  
Control Gain ◽  
Good Agreement

Abstract A nonlinear control system that can track the natural frequency of a MEMS resonator was developed in this study. Due to the evolution of fatigue damage, the natural frequency of the resonator decreases. To maintain the device at resonance, a phase-locked loop system is used to track the frequency decay and adjust the driving force accordingly. A model for the control system is introduced and the system behavior is analyzed using an averaging method. A quantitative criterion for selecting the control gain to achieve stability is derived from the analysis. Simulation results are shown to be in good agreement with the prediction of the theoretical analysis.

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